Sterile neutrino signals from supernovae

TL;DR

This paper explores how mixing between active and sterile neutrinos affects supernova neutrino flux ratios, providing insights into potential signals of sterile neutrinos in supernova observations.

Contribution

It introduces a numerical analysis of active-sterile neutrino mixing effects on supernova neutrino flux ratios using the density matrix formalism.

Findings

Flux ratios depend on active-sterile mixing angle.

Small mass gap influences neutrino flavor evolution.

Results can inform sterile neutrino detection in supernovae.

Abstract

We investigate the effects of a mixing of active and sterile neutrinos on the ratios of supernova electron neutrino flux ($F_e$) and antineutrino flux ($F_{\bar e}$) to the total flux of the other neutrino and antineutrino flavours ($F_a$). We assume that the heaviest (in the normal hierarchy) Standard Model neutrino $\nu_3$ mixes with a sterile neutrino resulting in a pair of mass eigenstates with a small mass gap. Using the density matrix formalism we solve numerically the the evolution of neutrino states in the envelope of a supernova and determine the flux ratios $F_e/F_a$ and $F_{\bar{e}}/F_a$ as a function of the active-sterile mixing angle and for the experimentally allowed range of the standard active-active mixing angle $\theta_{13}$.